The childbearing period is a critical life stage for excess weight gain and incident cardiometabolic disease, especially for the nearly three-quarters of African American women who enter pregnancy already overweight or obese. These women may be particularly disadvantaged, as they are at highest risk for retaining weight at the end of the first postpartum year, and notably begin gaining weight after 4-6 weeks' postpartum. Efforts to promote postpartum weight loss, however, have proven challenging. Relatively few weight loss studies have included ethnic minority women, and those that have - even when gold standard approaches are used - report less intervention engagement, higher attrition rates, and poorer postpartum weight loss outcomes among their African American participants. No fully powered trials have produced clinically meaningful weight loss in African American mothers over the first postpartum year. To remedy this evidence gap, our team of multidisciplinary researchers has spent the past half-decade partnering with African American mothers, primarily those of lower socioeconomic position, to develop an innovative, theory- and evidence-based postpartum obesity treatment that: 1) creates an energy deficit sufficient to produce weight loss by focusing on simple, empirically-supported obesogenic behavior change goals, tailored to the target population; and 2) uses low-cost, mobile technologies that enjoy high penetration among African American mothers (text messaging, mobile-optimized web pages and videos, social media) to deliver intervention content, promote social support, and allow for frequent yet convenient, interactive self-monitoring. To our knowledge, our 14-week pilot randomized controlled trial testing this novel approach is the only study that has demonstrated significant weight loss among low-income, African American mothers. The next step in this research is to examine whether we can translate the success of our promising K23-funded pilot study into a larger sample of obese, African American women, evaluated in the real-world setting of the Women, Infants and Children (WIC) Food and Nutrition Program of Philadelphia. WIC has a strong interest in addressing obesity and sees this intervention as a viable option for widespread dissemination among its ethnic minority participants. Thus, we propose to randomize 300 overweight or obese, African American WIC participants at 6 weeks' postpartum to either usual care (UC) or a community-based obesity treatment (OT) arm. The OT arm extends our postpartum obesity treatment program to 12 months, and includes expanded obesogenic behavior change goals, tailored skills training materials, interactive self-monitoring text messages, video testimonials, and interpersonal counseling support through health coach calls and Facebook. Assessments will be conducted at baseline, 6, and 12 months post baseline, with the primary outcome being weight loss at 12 months. If successful, the expected results could provide a sustainable, low-cost, postpartum weight loss intervention model for widespread dissemination to reduce disparities in obesity and cardiometabolic comorbidities.